Horizontal directional drilling (HDD), also known as directional boring or horizontal earth boring, involves using a surface drilling rig to install underground pipes, conduits, cables and any other utility in a shallow arc along a predefined bore path. This technique is so named due to its ability to be steered.
Using advanced controls and locating technologies, skilled operators can remotely guide the drill head to avoid obstacles and ensure that the bore path remains in compliance with engineering plans and specifications.
The origins of HDD can be traced back to the early 1960s, where a contractor by the name of Martin Cherrington developed the first HDD rig. However, It wasn’t until the early 1970s that the first river crossing was completed, representing a significant milestone in directional drilling and trenchless technology. (Read What Is Trenchless Technology.)
HDD is especially renowned for its ability to facilitate the construction and installation of underground utilities and structures with minimal impact on the surrounding environment. This attribute makes HDD ideal for installations in the vicinity of environmentally sensitive areas, i.e., areas that are protected due to their landscape, rich biodiversity, or historical value.
These locations include
- Wildlife habitat areas
- Forested areas
- Steep slopes
- Wetlands
- Waterways
- Prime agricultural lands
Conventional open-cut trenching, or excavations, occupy a large site footprint and can cause significant damage to environmentally sensitive areas. For construction activities near rivers and wetlands, excavations are also typically associated with costly weir, dam, and pier construction.
Urban environments are also negatively affected, as trenching can result in the destruction of existing above- and below- ground infrastructure, and traffic disruptions. Furthermore, excavation works are also typically accompanied by extensive and costly restoration and reinstatement of structures and infrastructure. (Learn more with 3 Reasons Slot Trenching Is the Preferred Excavation Method.)
Horizontal directional drilling, on the other hand, is a minimally invasive in situ construction technique that addresses the numerous environmental shortfalls of conventional excavation and trenching. HDD is trenchless, in other words, it does not require the construction of above-ground trenches; thus, making it the preferred construction method in areas where minimal disturbance of the environment is desired.
Horizontal bores and installations can be completed under steep or challenging terrain, wetlands, streams, rivers, and protected wildlife and forested zones with little to no impact on the surrounding area. In urban settings, this significantly reduced construction footprint lessens the adverse effects on above-ground structures and infrastructure. In some cases, installations can be even performed beneath residential areas with no evidence of construction appearing on the surface.
HDD can also significantly reduce the time for utility installation (simple horizontal bores can be completed in as little as one week). Additionally, HDD requires considerably less construction equipment than conventional trenching.
Faster construction times and less equipment translates to significantly lower construction costs, decreased energy consumption, and reduced greenhouse gas emissions.